You mentioned the main issue with this card -- it is almost entirely useless if there are no reactions on the board. I say "almost" because it could still be used with Conspirator, HoP, and even KC in a pinch, just like all cantrips. But other than that... it doesn't really do anything.
Some cards certainly do better within their sets. For example, Scout is better with other Intrigue cards, specifically Great Hall, Harem and Nobles.
But all cards still have SOME use, despite what is on the board. For example, Moat still has +2 cards which is functional even without attacks on the board.
I don't think there is a huge issue with nullifying reaction cards, but I think this needs something other than +1 Card, +1 Action.